Differential regulation of dentin sialophosphoprotein expression by Runx2 during odontoblast cytodifferentiation
Differential regulation of dentin sialophosphoprotein expression by Runx2 during odontoblast cytodifferentiation
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DOI：
10.1074/jbc.m502929200
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发表时间：
2005-08-19
影响因子：
4.8
通讯作者：
MacDougall, M
中科院分区：
文献类型：
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作者：
Chen, S;Rani, S;MacDougall, M
牙本质涎磷蛋白(DSPP)由牙本质唾液蛋白(DSP)和牙本质磷酸蛋白(DPP)组成。DSPP在牙体细胞分化过程中的时空表达受到很大限制。DSPP在牙齿发育中起着至关重要的作用。已知成骨细胞特异的转录因子Runx2对成骨细胞的分化是必不可少的。然而，Runx2对DSPP转录的影响仍不清楚。在这里，我们研究了Runx2在小鼠前成牙本质细胞(MD10-F2)和成牙本质细胞(MO6-G3)中调控DSPP表达的不同作用。原位杂交结果显示，在成牙本质细胞分化成熟过程中，DSPP的表达上调，而Runx2的表达下调。在小鼠和大鼠DSPP基因的启动子中存在三个潜在的Runx2位点。电泳迁移率改变分析和超位移实验表明，Runx2与这些位点结合。小鼠DSPP启动子Runx2位点突变导致MD10-F2细胞启动子活性下降，而在MO6-G3细胞启动子活性增加。在调节DSPP启动子方面，多个Runx2位点比单个位点更活跃。此外，强迫过表达Runx2亚型诱导了MD10-F2细胞内源性DSPP蛋白水平的增加，但降低了其在MO6-G3细胞中的表达，这与DSPP启动子分析一致。因此，我们的结果表明，Runx2对DSPP的不同正负调控依赖于牙齿外胚间充质来源细胞的细胞分化，这可能有助于DSPP在牙齿发育过程中的时空表达。
Dentin sialophosphoprotein (DSPP) consists of dentin sialoprotein (DSP) and dentin phosphoprotein (DPP). The spatial-temporal expression of DSPP is largely restricted during differentiational stages of dental cells. DSPP plays a vital role in tooth development. It is known that an osteoblast-specific transcription factor, Runx2, is essential for osteoblast differentiation. However, effects of Runx2 on DSPP transcription remain unknown. Here, we studied different roles of Runx2 in controlling DSPP expression in mouse preodontoblast (MD10-F2) and odontoblast (MO6-G3) cells. Two Runx2 isoforms were expressed in preodontoblast and odontoblast cells, and in situ hybridization assay showed that DSPP expression increased, whereas Runx2 was down-regulated during odontoblast differentiation and maturation. Three potential Runx2 sites are present in promoters of mouse and rat DSPP genes. Runx2 binds to these sites as demonstrated by electrophoretic mobility shift assay and supershift experiments. Mutations of Runx2 sites in mouse DSPP promoter resulted in a decline of promoter activity in MD10-F2 cells compared with an increase of its activity in MO6-G3 cells. Multiple Runx2 sites were more active than a single site in regulating the DSPP promoter. Furthermore, forced overexpression of Runx2 isoforms induced increases of endogenous DSPP protein levels in MD10-F2 cells but reduced its expression in MO6-G3 cells consistent with the DSPP promoter analysis. Thus, our results suggest that differential positive and negative regulation of DSPP by Runx2 is dependent on use of cytodifferentiation of dental ectomesenchymal-derived cells that may contribute to the spatial-temporal expression of DSPP during tooth development.